Jump to

Abstract

Near infrared spectroscopy can be used noninvasively and continuously to assess deep muscle pH (pHm) as an indicator of acidosis and adequacy of resuscitation. Since pHm is a new parameter, it was compared to blood measurements of arterial and venous pH (pHa, pHv) during shock in swine to provide data to aid in interpretation during clinical use.

Methods: Anesthetized 40 kg female swine (n=26) underwent hemorrhage until 24 mL/kg of blood was removed (Shock); followed by transection of the spleen causing uncontrolled hemorrhage throughout the remainder of the protocol. After 15min, 15.25mg/kg of resuscitation fluid (hextend, fresh frozen plasma or platelets) was given over 30min. Arterial and venous blood gases were measured at baseline, shock, end resuscitation and end of the study. Spectra were collected continuously from the posterior thigh muscle using a prototype CareGuide 1100 Oximeter. pHm was calculated from the spectra using the equation contained in the CareGuide 3100 product. Differences between survivors and non-survivors were assessed with two-way repeated measured ANOVA followed by a Tukey test.

RESULTS: Thirteen of the 26 swine did not survive for the full 5 hrs. pHv and pHm discriminated survivors and non-survivors at the end of resuscitation (p < 0.05) with lower pH for the non-survivors. pHa did not discriminate between survivors and non-survivors at any time point.

Conclusions: Noninvasive pHm is a surrogate for peripheral venous pH during swine hemorrhage and resuscitation.